Many proteins undergo varying degrees of modification during purification and storage. Certain proteins are known to be unusually susceptible to thermal denaturation or to proteolytic cleavage; others contain reactive amino acid side chains, which due to their location within the tertiary structure of the protein, are particularly susceptible to chemical modification, including oxidation. While the tertiary structure of the protein, if known, may suggest what forces can be used in its stabilization, it is generally not possible to predict the extent to which any of the modifications will occur.
It is also known that various metals can act as catalysts of oxidation. Due to the ease with which such products are oxidized, antioxidants are frequently required to stabilize proteins in a pharmaceutical formulation.
Basic fibroblast growth factor (bFGF) is currently undergoing clinical trials for wound healing indications. Although early preparations were shown to be biologically active through in vitro cell assay, formulations of nonreduced bFGF produced heterogeneous mixtures, and it was discovered that multimers of reduced bFGF were formed after short-term storage at room temperature, under refrigeration, or in the frozen state. In addition, more sophisticated analytical techniques such as quasi-elastic light-scattering techniques and UV spectroscopy, have revealed that insoluble aggregates can form in aged solution formulations at higher bFGF concentrations (1 mg/ml or greater) and in lyophilized formulations.
In light of these discoveries, it would be desirable to provide pharmaceutical formulations of bFGF that overcome these problems by providing compositions that improve the stability of bFGF both in solution and in lyophilized form.